It is well-known that solids that are difficult to sediment are sedimented in large stilling containers over quite a long period. In the moment where the solids are drawn off, they are swirled back into the liquid, so that it becomes necessary for the sediment to settle again. To support sedimentation, stilling plates are introduced into the liquid.
It is known from waterworks sludges that a conditioning of waterworks sludges in stationary ultrasonic fields leads to improved sedimentation and to a faster purification of the fluid phase.